As far as I know, malaria is spread by mosquitos and they are everywhere in the tropics. Traveled to lots of islands and been to almost every tourist spot in the mexican tropics...never heard of a malaria warning. If you are still concerned, visit the CDC website and look for info.
I'm going to these same spots in 7 weeks, not worried a bit! :o)
Check with the local health dept. I have seen this question asked before, but I don't know of anyone who has taken the shots. I am under the impression the shots are only recommended for those who are traveling into the jungle or are spending an extended period of time in these places,not a few hours. We have been to Belize twice and Roatan 4 times, never considered the shots. I would recommend using some repellant with DEET in it because the sand flies in Roatan can't be seen, but sure can be felt if they decide you will make a good dinner. these are desease carrying, just a pain in the wherever they get you. NMNita